Cars are still the number one way to smuggle marijuana out of Colorado, according to the report, which partly draws on data voluntarily submitted by various law enforcement agencies. Last year, authorities seized 3,690 pounds of marijuana, a 33 percent increase from 2012.

The vast majority of marijuana was transported by car eastward. The largest number of pot seizures was in Missouri, where 41 were reported in 2013. The next closest state is Texas with 18.

The report predicts that the amount of marijuana, in pounds, will decrease in coming years, as highly potent marijuana oils, waxes, and edibles are easier to hide and are more lucrative for traffickers.